this is great news!
The echogenic area with irregular borders is the corpus luteum
- which stay behind after the cyst
has ovulated - it`s the remains of the fiollicle. So the follicle after erruption/ ovulation.
This corpus luteum produced hormones esp. progesterone
- which stops the menstraution until the fertilized egg nestles in and produces HCG , the pregnancy
hormone, which also stops any bleeding.
If the egg doesn`t get fertilized expect a period in approx. 2 weeks time.
The endoemtrium lining of 8mm shows that you had good estrogene levels.
All sounds good to me!